U.S. Pat. No. 5,631,892 deals with the deterioration of the wobble/noise ratio due to a deviation in the positioning of the detector. A solution is described to cancel the resulting noise. It consists in adjusting a weighting ratio between the two signals that are detected and that contribute to the wobble signal so as to make the DC component of the wobble signal equal to zero. This solution is based on the assumption that the noise component in the wobble signal is proportional to the deviation of the detector position.
This assumption cannot be held for some types of aberrations that also lead to radial asymmetry in the two halves of the detector, and therefore to a leakage of data in the wobble signal.
An object of the invention is to propose a solution for eliminating the noise of various origins in the wobble signal, notably the high-frequency data leakage into the wobble signal due to radial asymmetry introduced in the diffraction pattern on the detector, whatever the reason for this radial asymmetry.